An aqueous dispersion containing fluoropolymer particles can be formed into a film with excellent characteristics such as chemical stability, non-adhesion, and weather resistance, by coating, impregnation, or other methods, and is therefore widely used, for example, for cooking equipment, lining of pipes, and glass fiber cloth impregnation film.
Patent Literature 1 discloses an aqueous fluororesin dispersion containing fluororesin particles and a nonionic surfactant, and further discloses that condensation is accelerated by adding ammonium laurate, triethanolamine laurate, sodium lauryl sulfate, ammonium lauryl sulfate, triethanolamine lauryl sulfate, or the like in an amount of not more than 0.2% by mass based on the amount of the fluororesin.
Patent Literature 2 discloses a method for reducing a fluorosurfactant content of an aqueous fluoropolymer dispersion containing a fluorosurfactant, which is stabilized with a nonionic surfactant, and further discloses that any of various non-fluorinated anionic surfactants may be used. Examples of the non-fluorinated anionic surfactants include, but are not limited to, sodium lauryl sulfate, sodium dodecylbenzylsulfonate, and secondary sodium alkyl sulfonate. The non-fluorinated anionic surfactants are particularly preferably ammonium lauryl sulfate or alkali metals, and most preferably sodium lauryl sulfate.
Patent Literature 3 discloses a production method of an aqueous fluoropolymer dispersion, which involves bringing an aqueous fluoropolymer dispersion containing a fluoropolymer, a fluorine-containing emulsifier, and a specific organic carboxylic acid into contact with a weakly basic anion-exchange resin, thereby adsorbing and removing the fluorine-containing emulsifier; and bringing the resulting aqueous fluoropolymer dispersion into contact with a strongly basic anion-exchange resin, thereby adsorbing and removing the organic carboxylic acid. Patent Literature 3 further discloses that an anionic surfactant other than the fluorine-containing emulsifier may be added before or after condensation in order to improve the stability and condensation rate. Examples of the anionic surfactant include ammonium laurate, ethanolamine laurate, ammonium cinnamate, ammonium lauryl sulfate, sodium lauryl sulfate, triethanolamine lauryl sulfate, and p-t-butyl ammonium benzoate.